Antifog/barrier laminate for use in meat packaging

ABSTRACT

A multilayered packaging film having good antifog performance that is suitable for use in food packaging. The multilayered film comprises a nylon film having first and second surfaces; a sealant film positioned on the first surface of the nylon film, either directly on the first surface of the nylon film or via an intermediate adhesive; an antifog composition contained within at least part of the sealant film or coated on a surface of the sealant film opposite the nylon film; and a protective film applied onto the second surface of the nylon film.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to packaging films. More particularly, theinvention pertains case ready packaging films having good antifogperformance that are suitable for use in meat packaging.

[0003] 2. Description of the Related Art

[0004] Containers have long been used to store perishable foods, such asmeats, fruits and vegetables, prior to sale in the marketplace toconsumers. Maximizing the time in which the food remains preserved inthe containers minimizes the amount of spoilage.

[0005] The environment around which the food is preserved is animportant factor in the preservation process. It is important that thefood is maintained at an adequate temperature, while also controllingthe molecular and chemical content of the gases surrounding the food. Byproviding an appropriate gas content to the environment surrounding thefood, the food can be better preserved when maintained at the propertemperature or even when it is exposed to variations in temperature.This gives the food producer some assurance that the food will be in anacceptable condition when it reaches the consumer. Preferred modifiedatmosphere packaging systems for foods, including raw meats, exposesthese foods to extremely low levels of oxygen because it is well knownthat the freshness of meat can be preserved longer under anaerobicconditions than under aerobic conditions. Maintaining low levels ofoxygen minimizes the growth and multiplication of aerobic bacteria.Additionally, modified atmosphere packaging can involve high levels ofoxygen (80%) combined with nitrogen and/or carbon dioxide. The gases inthese combinations do not favor bacterial growth but allow the raw meatto maintain a preferred red color that is acceptable to the consumer.

[0006] It is also important that the packaging exhibit good resistanceto the formation of condensation inside the package on a surface of thefilm. This is known in the art as an antifog property. Multilayeredfilms for modified atmosphere packaging having such antifog propertiesare well known and are commonly used when packaging food products havinga high moisture content, such as fresh meats, and when it is importantfor the product to be clearly visible to the consumer. For example, U.S.Pat. No. 5,766,772 describes multi-layer heat-shrinkable films endowedwith antifog properties having a different structure from thisinvention.

[0007] To produce a film exhibiting this antifog property, an antifogcomponent is typically blended with or coated onto a sealant film suchas a polyethylene film. This antifog-polyethylene component then forms apart of a multilayered packaging film, such as a nylon packaging film,that may also incorporate an oxygen barrier polymer layer such asethylene vinyl alcohol. However, one significant problem associated withsuch known multilayered films having this antifog component is that theantifog component tends to be drawn toward polar materials, such asnylon, and away from the non-polar polyethylene. This is particularly aproblem when the film is rolled up after manufacture such that theantifog layer or antifog containing polyethylene layer is brought intodirect contact with an adjacent nylon layer. This causes the antifogcomponent to migrate out of its existing polyethylene layer and into thenylon layer, compromising the performance of the nylon layer as well asdegrading the antifog property of the film. Therefore, it would bedesirable to have a multilayered packaging film having good antifogperformance and having an antifog component which does not migrate intoadjacent nylon layers when stored. The present invention provides such asolution to this need.

SUMMARY OF THE INVENTION

[0008] The invention provides a multilayered film comprising:

[0009] a) a nylon film having first and second surfaces;

[0010] b) a sealant film, positioned on the first surface of the nylonfilm, either directly on the first surface of the nylon film or via anintermediate adhesive;

[0011] c) an antifog composition contained within at least part of thesealant film or coated on a surface of the sealant film opposite thenylon film; and

[0012] d) a protective film applied onto the second surface of the nylonfilm.

[0013] The invention also provides a multilayered film comprising:

[0014] a) a first nylon layer having first and second surfaces;

[0015] b) an ethylene vinyl alcohol layer positioned on the firstsurface of the nylon layer;

[0016] c) a second nylon layer positioned on a surface of the ethylenevinyl alcohol layer opposite the first nylon layer;

[0017] d) a polyethylene sealant film, positioned on a surface of thesecond nylon layer which is opposite to the ethylene vinyl alcohollayer;

[0018] e) an antifog composition contained within the sealant film orcoated on a surface of the sealant film which is opposite the secondnylon layer; and

[0019] f) a polyurethane protective film applied on the second surfaceof the first nylon film.

[0020] The invention further provides a process for forming amultilayered film comprising:

[0021] a) positioning a sealant film onto a first surface of a nylonfilm, wherein the sealant film has an antifog composition which iseither incorporated therein or coated on a surface of the sealant filmopposite the nylon film; and

[0022] b) applying a protective film onto a second surface of the nylonfilm.

[0023] The invention still further provides a food package whichcomprises a container having an open portion and a multilayered filmsealing the open portion, which multilayered film comprises:

[0024] a) a nylon film having first and second surfaces;

[0025] b) a sealant film, positioned on the first surface of the nylonfilm, either directly on the first surface of the nylon film or via anintermediate adhesive;

[0026] c) an antifog composition contained within at least part of thesealant film or coated on a surface of the sealant film opposite thenylon film; and

[0027] d) a protective film applied onto the second surface of the nylonfilm; the multilayered film being positioned such that the protectivefilm is away from the open portion of the container.

[0028] The invention therefore provides a desirable multilayeredpackaging film having good antifog performance and having an antifogcomponent which does not migrate into adjacent nylon layers when stored.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The invention provides a multilayered packaging film having goodantifog properties wherein the antifog composition does not migrate intoadjacent polar film layers. In the production of a multilayered filmaccording to the invention, a nylon film having first and secondsurfaces is positioned on a surface of a sealant film, either directlyon the first surface of the nylon film or via an intermediate adhesivelayer. An antifog composition is contained within at least part of thesealant film or coated on a surface of the sealant film that is oppositeto the nylon film, i.e. a surface different than the surface to whichthe nylon film is attached. A protective film is also applied onto thesecond surface of the nylon film opposite the sealant film. This filmexhibits good, permanent antifog properties and avoids migration of theantifog composition out of the sealant film.

[0030] Nylons are conventionally used in the art of multilayeredpackaging films. Suitable nylons within the scope of the inventionnon-exclusively include homopolymers or copolymers selected fromaliphatic polyamides and aliphatic/aromatic polyamides having amolecular weight of from about 10,000 to about 100,000. Generalprocedures useful for the preparation of polyamides are well known tothe art. Such include the reaction products of diacids with diamines.Useful diacids for making polyamides include dicarboxylic acids whichare represented by the general formula

HOOC—Z—COOH

[0031] wherein Z is representative of a divalent aliphatic radicalcontaining at least 2 carbon atoms, such as adipic acid, sebacic acid,octadecanedioic acid, pimelic acid, suberic acid, azelaic acid,dodecanedioic acid, and glutaric acid. The dicarboxylic acids may bealiphatic acids, or aromatic acids such as isophthalic acid andterephthalic acid. Suitable diamnines for making polyamides includethose having the formula

H₂N(CH₂)_(n)NH₂

[0032] wherein n has an integer value of 1-16, and includes suchcompounds as trimethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, octamethylenediamine,decamethylenediamine, dodecamethylenediamine, hexadecamethylenediamine,aromatic diamines such as p-phenylenediamine, 4,4′-diaminodiphenylether, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenylmethane,alkylated diamines such as 2,2-dimethylpentamethylenediamine,2,2,4-trimethylhexamethylenediamine, and 2,4,4trimethylpentamethylenediamine, as well as cycloaliphatic diamines, suchas diaminodicyclohexylmethane, and other compounds. Other usefuldiamines include heptamethylenediamine, nonamethylenediamine, and thelike.

[0033] Useful polyamide homopolymers include poly(4-aminobutyric acid)(nylon 4), poly(6-aminohexanoic acid) (nylon 6, also known aspoly(caprolactam)), poly(7-aminoheptanoic acid) (nylon 7),poly(8-aminooctanoic acid)(nylon 8), poly(9-aminononanoic acid) (nylon9), poly(10-aminodecanoic acid) (nylon 10), poly(11-aminoundecanoicacid) (nylon 11), poly(12-aminododecanoic acid) (nylon 12), nylon 4,6,poly(hexamethylene adipamide) (nylon 6,6), poly(hexamethylenesebacamide) (nylon 6,10), poly(heptamethylene pimelamide) (nylon 7,7),poly(octamethylene suberamide) (nylon 8,8), poly(hexamethyleneazelamide) (nylon 6,9), poly(nonamethylene azelamide) (nylon 9,9),poly(decamethylene azelamide) (nylon 10,9),poly(tetramethylenediamine-co-oxalic acid) (nylon 4,2), the polyamide ofn-dodecanedioic acid and hexamethylenediamine (nylon 6,12), thepolyamide of dodecamethylenediamine and n-dodecanedioic acid (nylon12,12) and the like. Useful aliphatic polyamide copolymers includecaprolactam/hexamethylene adipamide copolymer (nylon 6,6/6),hexamethylene adipamide/caprolactam copolymer (nylon 6/6,6),trimethylene adipamide/hexamethylene azelaiamide copolymer (nylontrimethyl 6,2/6,2), hexamethylene adipamide-hexamethylene-azelaiamidecaprolactam copolymer (nylon 6,6/6,9/6) and the like. Also included areother nylons which are not particularly delineated here. Of thesepolyamides, preferred polyamides include nylon 6, nylon 6,6, nylon 6/6,6as well as mixtures of the same.

[0034] Aliphatic polyamides used in the practice of this invention maybe obtained from commercial sources or prepared in accordance with knownpreparatory techniques. For example, poly(caprolactam) can be obtainedfrom Honeywell International Inc., Morristown, N.J. under the trademarkCAPRON®.

[0035] Exemplary of aliphatic/aromatic polyamides includepoly(tetramethylenediamine-co-isophthalic acid) (nylon 4,I),polyhexamethylene isophthalamide (nylon 6,I), hexamethyleneadipamide/hexamethylene-isophthalamide (nylon 6,6/6I), hexamethyleneadipamide/hexamethylene-terephthalamide (nylon 6,6/6T), poly(2,2,2-trimethyl hexamethylene terephthalamide), poly(m-xylyleneadipamide) (MXD6), poly(p-xylylene adipamide), poly(hexamethyleneterephthalamide), poly(dodecamethylene terephthalamide), polyamide6T/6I, polyamide 6/MXDT/I, polyamide MXDI, and the like. Blends of twoor more aliphatic/aromatic polyamides can also be used.Aliphatic/aromatic polyamides can be prepared by known preparativetechniques or can be obtained from commercial sources. Other suitablepolyamides are described in U.S. Pat. Nos. 4,826,955 and 5,541,267,which are incorporated herein by reference.

[0036] Positioned on a surface of the nylon film is a heat sealablesealant film which improves the ability of the multilayered film to besealed onto a package. The sealant film is preferably comprised ofpolyethylene, and has an antifog composition that is either combinedwith the polyethylene or coated on a surface of the sealant filmopposite the nylon film. Non-limiting examples of suitable polyethylenesare low density polyethylene (LDPE), linear low density polyethylene(LLDPE), linear medium density polyethylene (LMDPE), linear very-lowdensity polyethylene (VLDPE), linear ultra-low density polyethylene(ULDPE), metallocene linear low density polyethylene (MLLDPE) highdensity polyethylene (HDPE). Of these, the most preferred is linear lowdensity polyethylene.

[0037] The antifog composition prevents condensation on the film whenused to package products such as fresh meats, vegetables, etc.Non-limiting examples of antifog compositions are glycerol monoesters ofa saturated or unsaturated fatty acid having from about 8 to about 20carbon atoms, glycerol diesters of a saturated or unsaturated fatty acidhaving from about 8 to about 20 carbon atoms and ionic surfactantshaving phosphate, sulfate or quatemary amine functional end groups. Alsosuitable as antifog compositions are surfactants including anionic,cationic, nonionic and amphoteric surfactants. Suitable ionicsurfactants have phosphate, sulfate or quaternary amine functional endgroups. Other antifog compositions include sorbitan esters of aliphaticcarboxylic acids, glycerol esters of aliphatic carboxylic acids, estersof other polyhydric alcohols with aliphatic carboxylic acids,polyoxyethylene compounds, such as the polyoxyethylene sorbitan estersof aliphatic carboxylic acids and polyoxyethylene ethers of higheraliphatic alcohols. Preferred antifog compositions are glycerolmonooleate, glycerol monostearate, sorbitan esters and blends thereof.When the antifog composition is incorporated into the sealant film, itis blended into the polyethylene composition preferably in an amount offrom about 0.1 weight percent to about 5 weight percent. When theantifog composition is coated on the sealant film it is preferablyapplied at a coating weight of from about 0.2 to about 0.6 g/m².Suitable antifog compositions are described, for example, in U.S. Pat.No. 5,766,772.

[0038] In an alternate embodiment of the invention, the sealant film maybe comprised of a combination of various individual layers in additionto polyethylene. For example, the sealant film may comprise a structurecomprising a heat sealable first polyethylene layer, an ethylene vinylalcohol layer, a second polyethylene layer and an antifog layer (or anantifog composition containing second polyethylene layer). In yetanother embodiment, the sealant film may comprise a structure comprisinga polyolefin layer, a first polyethylene layer, an adhesive tie layer,an ethylene vinyl alcohol layer, another adhesive tie layer, a secondpolyethylene layer and an antifog composition containing thirdpolyethylene layer. These structures may be formed either by laminationor by coextrusion of the individual layers.

[0039] In the latter embodiment, suitable polyolefins include polymersof alpha-olefin monomers having from about 2 to about 6 carbon atoms andincludes homopolymers, copolymers (including graft copolymers), andterpolymers of alpha-olefins. Illustrative homopolymer examples includeultra low density (ULDPE), low density (LDPE), linear low density(LLDPE), medium density (MDPE), or high density polyethylene (HDPE);polypropylene; polybutylene; polybutene-1; poly-3-methylbutene-1;poly-pentene-1; poly-4-methylpentene-1; polyisobutylene; and polyhexene.

[0040] Polyolefins such as polyethylenes are commonly differentiatedbased on the density which results from their numbers of chain branchesper 1,000 carbon atoms in the polyethylene main chain in the molecularstructure. Branches typically are C₃-C₈ olefins, and which arepreferably butene, hexene or octene. For example, HDPE has very lownumbers of short chain branches (less than 20 per 1,000 carbon atoms),resulting in a relatively high density, i.e. density ranges from about0.94 gm/cc to about 0.97 gm/cc. LLDPE has more short chain branches, inthe range of 20 to 60 per 1,000 carbon atoms with a density of about0.91 to about 0.93 gm/cc. LDPE with a density of about 0.91 to about0.93 gm/cc has long chain branches (20-40 per 1,000 carbon atoms)instead of short chain branches in LLDPE and HDPE. ULDPE has a higherconcentration of short chain branches than LLDPE and HDPE, i.e. in therange of about 80 to about 250 per 1,000 carbon atoms and has a densityof from about 0.88 to about 0.91 gm/cc.

[0041] Illustrative copolymer and terpolymers include copolymers andterpolymers of alpha-olefins with other olefins such asethylene-propylene copolymers; ethylene-butene copolymers;ethylene-pentene copolymers; ethylene-hexene copolymers; andethylene-propylene-diene copolymers (EPDM). Preferred polyolefins arethose prepared from alpha-olefins, and are most preferably ethylenepolymers, copolymers, and terpolymers. The above polyolefins may beobtained by any known process. The polyolefin may have a weight averagemolecular weight of about 1,000 to about 1,000,000, and preferably about10,000 to about 500,000. Preferred polyolefins are polyethylene,polypropylene, polybutylene and copolymers, and blends thereof. The mostpreferred polyolefin is polyethylene.

[0042] Suitable polyethylenes are those described above. Thispolyethylene layer may be attached to an ethylene vinyl alcohol layer,preferably via an intermediate adhesive tie layer. Suitable adhesivematerials include polyurethanes, epoxies, polyesters, acrylics,anhydride modified polyolefin and blends thereof. Modified polyolefincompositions have at least one functional moiety preferably selectedfrom the group consisting of unsaturated polycarboxylic acids andanhydrides thereof. Such unsaturated carboxylic acid and anhydridesinclude maleic acid and anhydride, fumaric acid and anhydride, crotonicacid and anhydride, citraconic acid and anhydride, itaconic acid ananhydride and the like. The adhesive layer may also optionally comprisea colorant, an ultraviolet light absorber or both. The adhesive layermay be applied either directly onto the nylon film or onto thepolyethylene layer by any appropriate means in the art, such as bycoating.

[0043] Ethylene vinyl alcohol compounds are well known in the art andreadily commercially available. Copolymers of ethylene and vinyl alcoholsuitable for use in the present invention can be prepared, for example,by the methods disclosed in U.S. Pat. Nos. 3,510,464; 3,560,461;3,847,845; 3,595,740 and 3,585,177. The ethylene vinyl alcohol copolymercan be a hydrolyzed ethylene vinyl acetate copolymer. The degree ofhydrolysis can range from about 85% to about 99.5%. The ethylene vinylalcohol copolymer preferably contains from about 15 to about 65 molpercent ethylene and more preferably about 25 to about 50 mol percentethylene. Copolymers of lower than 15 mol percent ethylene tend to bedifficult to extrude while those above 65 mol percent ethylene havereduced oxygen barrier performance. The term “ethylene/vinyl alcoholcopolymer” or “EVOH” is intended to comprise also the hydrolyzed orsaponified ethylene/vinyl acetate copolymers and refers to a vinylalcohol copolymer having an ethylene comonomer, which may be obtained,for example, by the hydrolysis of an ethylene/vinyl acetate copolymer orby chemical reaction of ethylene monomers with vinyl alcohol.

[0044] Applied onto an opposite surface of the nylon film is aprotective film. This protective film may comprise a material selectedfrom the group consisting of polyurethane, polyvinylidene chloride (withor without a primer), acrylics, polyester polyols, and amine modifiedpolyurethanes. Suitable primers include acrylics, urethanes, polyesterpolyols or amine modified polyurethanes.

[0045] These materials may be crosslinked with suitable crosslinkingagents as is well known in the art. Suitable crosslinking agents includebut are not limited to aromatic diisocyanates, such as toluenediisocyanate, aliphatic diisocyanates, such as hexamethylenediisocyanate, glycol adducts of isocyanates, prepolymers made fromisocyanate monomers and butylated-melamine or methylated-melamineformaldehydes. In an additional embodiment of the invention, a layer ofa polyvinylidene chloride may optionally be applied onto a surface ofthe protective film that is not adjacent to the nylon film.

[0046] In the preferred embodiment of the invention the protective filmis coated onto the outer surface of the nylon film which is opposite thesurface at which the sealant film is attached. Suitable coating methodsinclude dip coating, meniscus coating, roller coating, doctor bladecoating, and the like which are well known in the art.

[0047] Each of the nylon film, sealant film and protective film mayoptionally also include one or more conventional additives whose usesare well known to those skilled in the art. The use of such additivesmay be desirable in enhancing the processing of the compositions as wellas improving the products or articles formed therefrom. Examples of suchinclude: oxidative and thermal stabilizers, lubricants, release agents,flame-retarding agents, oxidation inhibitors, oxidation scavengers,dyes, pigments and other coloring agents, ultraviolet light absorbersand stabilizers, organic or inorganic fillers including particulate andfibrous fillers, reinforcing agents, nucleators, plasticizers, as wellas other conventional additives known to the art. Such may be used inamounts, for example, of up to about 10% by weight of the overallcomposition. Representative ultraviolet light stabilizers includevarious substituted resorcinols, salicylates, benzotriazole,benzophenones, and the like. Suitable lubricants and release agentsinclude stearic acid, stearyl alcohol, and stearamides. Exemplaryflame-retardants include organic halogenated compounds, includingdecabromodiphenyl ether and the like as well as inorganic compounds.Suitable coloring agents including dyes and pigments include cadmiumsulfide, cadmium selenide, titanium dioxide, phthalocyanines,ultramarine blue, nigrosine, carbon black and the like. Representativeoxidative and thermal stabilizers include the Period Table of Element'sGroup I metal halides, such as sodium halides, potassium halides,lithium halides; as well as cuprous halides; and further, chlorides,bromides, iodides. Also, hindered phenols, hydroquinones, aromaticamines as well as substituted members of those above mentioned groupsand combinations thereof. Exemplary plasticizers include lactams such ascaprolactam and lauryl lactam, sulfonamides such aso,p-toluenesulfonamide and N-ethyl, N-butyl benzylnesulfonamide, andcombinations of any of the above, as well as other plasticizers known tothe art.

[0048] Each of the layers may be joined together by coextrusion. In thecoextrusion process, for example, the polymeric material for theindividual layers are fed into infeed hoppers of a like number ofextruders, each extruder handling the material for one or more of thelayers. The melted and plasticated streams from the individual extrudersare fed into a single manifold co-extrusion die. While in the die, thelayers are juxtaposed and combined, then emerge from the die as a singlemultiple layer film of polymeric material. After exiting the die, thefilm is cast onto a first controlled temperature casting roll, passesaround the first roll, and then onto a second controlled temperatureroll, which is normally cooler than the first roll. The controlledtemperature rolls largely control the rate of cooling of the film afterit exits the die. Additional rolls may be employed. In another method,the film forming apparatus may be one which is referred to in the art asa blown film apparatus and includes a multi-manifold circular die headfor bubble blown film through which the plasticized film composition isforced and formed into a film bubble which may ultimately be collapsedand formed into a film. Processes of coextrusion to form film and sheetlaminates are generally known. Typical coextrusion techniques aredescribed in U.S. Pat. Nos. 5,139,878 and 4,677,017.

[0049] Alternately the individual films may first be formed as separatelayers and then laminated together under heat and pressure with orwithout intermediate adhesive layers. Lamination techniques are wellknown in the art. Typically, laminating is done by positioning theindividual layers on one another under conditions of sufficient heat andpressure to cause the layers to combine into a unitary film. Typicallythe nylon film and the antifog composition containing sealant film willbe positioned on one another, and the combination is passed through thenip of a pair of heated laminating rollers by techniques well known inthe art. Lamination heating may be done at temperatures ranging fromabout 120° C. to about 175° C., preferably from about 150° C. to about175° C., at pressures ranging from about 5 psig (0.034 MPa) to about 100psig (0.69 MPa), for from about 5 seconds to about 5 minutes, preferablyfrom about 30 seconds to about 1 minute. Further, when the sealant filmcomprises the multilayered structure described above, it is preferredthat the individual layers are laminated together. However, it is mostpreferred that the nylon film be coextruded.

[0050] In one embodiment of the invention, the nylon film is orientedprior to being attached to the sealant film. For the purposes of thepresent invention the term draw ratio is an indication of the increasein the dimension in the direction of draw. Preferably, in the presentinvention the nylon film is drawn to a draw ratio of from 1.5:1 to 5:1uniaxially in at least one direction, i.e. its longitudinal direction,its transverse direction or biaxially in each of its longitudinal andtransverse directions. Preferably, the nylon film is simultaneouslybiaxially oriented, for example orienting a plasticized film in both themachine and transverse directions at the same. This results in dramaticimprovements in clarity strength and toughness properties. Preferably,the nylon film is biaxially oriented and is not heat set so that it isshrinkable both in its transverse and longitudinal directions.

[0051] Although each layer of the multilayer film structure may have adifferent thickness, the thickness of the nylon film is preferably fromabout 1 μm to about 25 μm, more preferably from about 3 μm to about 8μm, and most preferably from about 4 μm to about 6 μm. The thickness ofthe protective film is preferably from about 1 μm to about 25 μm, morepreferably from about 2 μm to about 8 μm and most preferably from about3 μm to about 5 μm. The thickness of the sealant film is preferably fromabout 1 μm to about 50 μm, more preferably from about 10 μm to about 30μm, and most preferably from about 12 μm to about 25 μm. If amulticomponent sealant film is included rather than an individualantifog containing polyethylene layer, the thickness of thatmulticomponent sealant film is preferably within this range. While suchthicknesses are preferred, it is to be understood that other filmthicknesses may be produced to satisfy a particular need and yet fallwithin the scope of the present invention.

[0052] The oxygen transmission rate (OTR) of the multilayered film ofthe invention may be determined via the procedure of ASTM D-3985. In thepreferred embodiment, the multilayered film according to this inventionhas an OTR of about 0.5 cc/100 in²/day or less, preferably from about0.1 cc/100 in²/day or less and more preferably from about 0.05 cc/100in²/day or less at 65% relative humidity at 20° C.

[0053] The multilayered film of the invention is preferably heatshrinkable, generally by an amount of from about 2% to about 30%, morepreferably from about 10% to about 20% in its length, or its width oreach of its length and width. To provide a tightly adhering lid for atray, for example, the film only need to exhibit shrinkage on the orderof about 2 to about 3%. However, in order to have the film also -form(unrestrained) about the side of the tray, higher shrinkage in the filmis desirable. The multilayered film may further have printed indicia onthe nylon film. Since such printing is on an internal surface of thestructure, it will not rub off when the surface is contacted.Optionally, the multilayered film may be uniaxially or biaxiallyoriented in a manner and in an amount indicated above for the nylon filmand is not heat set so that it is shrinkable both in its transverse andlongitudinal directions. In this case the nylon film may or may not havebeen oriented already.

[0054] The film preferably has a puncture resistance of at least about10 lbs. force as measured by ASTM F 1306, and preferably higher than 10lbs. force. Preferably the film has a haze of about 4% or less and aclarity of about 92% or higher as measured by ASTM DI 003.

[0055] The multilayered film may be formed into and stored as a roll. Ithas been found that the unique structure of this inventive film isparticularly effective in preventing the migration of the antifogmaterial from the polyethylene of the sealant film to the nylon filmwhen in roll form.

[0056] The multilayered film is useful for forming a food packageincluding a container, such as a tray, having an open portion and themultilayered film sealing the open portion. Such a structure isgenerally referred to a lidding or packaging film. Such containers aresuitable for packaging a variety of raw meats such as beef, pork,poultry, and veal, among others. A packaged food may comprises the foodpackage and a food product such as a meat in the food package.

[0057] The container may have enclosed side walls, a floor and an topopening defining a central cavity wherein the open top optionally has asubstantially flat peripheral rim. The multilayered film surrounds thecontainer and is heat shrunk and heat sealed to it such that the antifogcomposition is on the open portion (facing inward) and the protectivefilm is facing away from the open portion of the container. Thecontainer may comprise a material such as cardboard, paperboard,boardstock, a plastic and combinations thereof. Preferred plasticsinclude any one of several thermosetting or thermoplastic resins any ofwhich are capable of sealing to the lidding material. Examples ofmaterials include acrylonitrile, an acrylic polymer, polyethyleneterephthalate (PET) or copolymers thereof, polyvinyl chloride,polycarbonate, polystyrene and polypropylene. In use the multilayeredfilm is positioned around the open portion and is caused to shrink, e.g.by the application of heat, by a sufficient amount to seal the openportion of the container.

[0058] The invention further contemplates additional layers beingattached to the multilayered film either before or after attaching thenylon film. For example, the nylon film of the invention may comprise asingle nylon layer, or may also comprise additional layers. Inparticular, the nylon film may comprise a structure comprising a firstnylon layer, an ethylene vinyl alcohol layer and a second nylon layer.In this embodiment, an ethylene vinyl alcohol layer is positioned onto afirst surface of a first nylon layer, a second nylon layer is positionedon a surface of the ethylene vinyl alcohol layer opposite the firstnylon layer, a sealant film is positioned on a surface of the secondnylon layer opposite the ethylene vinyl alcohol layer, and a protectivefilm is applied on a second surface of the first nylon film.Additionally, an antifog composition is preferably either containedwithin at least part of the sealant film or coated on a surface of thesealant film opposite the second nylon layer. In this embodiment, eachof the layers are preferably attached by coextrusion, but may also beattached by lamination with or without an intermediate adhesive layer.

[0059] The following non-limiting examples serve to illustrate theinvention.

EXAMPLES

[0060] In the following examples, the sealant film is a monolayer filmof a metallocene linear low density polyethylene. The polyethylene isblended with an antifog-containing polyethylene masterbatch prior toextrusion. The material is dry laminated to a variety of nylon films(coated and uncoated) using a two component polyurethane adhesiveapplied to the nylon film.

[0061] Evidence for antifog migration is measured by the surface contactangle of water on both the polyethylene and nylon surfaces. The antifogperformance is determined from a modification of a cold fog testprocedure. Film is stretched over a polypropylene tray containing 30 mlof water soaked into a paper towel. The package is placed in arefrigerator at 4° C. and monitored for a period of 24 hours. At givenintervals the inside surface of the film is visually examined and ratedaccording to the following, with a score of above 8 being acceptable:Grade Antifog Performance 0 Fine fog across entire surface. Difficult toview product 2 Small droplets (1-2 mm). Product somewhat obscured. 4Medium droplets (2-4 mm). 6 Large drops (>4 mm). 8 Moisture visible butfairly uniform w/some texture or large drops. 10 Indistinguishable fromdry film over entire package.

Example 1 (Comparative)

[0062] The sealant film (with either 20% or 40% antifog masterbatchadded) was laminated to a film of biaxially oriented nylon 6 (Capran®Emblem available from Honeywell International Inc.), formed into a roll,and left to sit for a period of 72 hours. The results are shown below:20% Antifog 40% Antifog Material Test Data Masterbatch Masterbatch AsMade PE Surface Contact Angle  <10°  <10° Antifog Performance Rating 8 9After PE Surface Contact Angle 39.3° 29° Contact Antifog PerformanceRating 6 6

Example 2

[0063] The sealant film (with either 20% or 40% antifog masterbatchadded) was laminated to a film of polyvinylidene chloride (PVdC) coated,biaxially oriented nylon 6 (Capran® Emblem), formed into a roll, andleft to sit for a period of 72 hours. The PVdC had a polyurethane primercoating. The results are shown below: 20% Antifog 40% Antifog MaterialTest Data Masterbatch Masterbatch As Made PE Surface Contact Angle <10°<10° Antifog Performance Rating 8  9 After PE Surface Contact Angle33.3° 32.3° Contact Antifog Performance Rating 8 10

Example 3

[0064] The sealant film (with either 20% or 40% antifog masterbatchadded) was laminated to a film of polyurethane coated, biaxiallyoriented nylon 6 (Capran® Emblem), formed into a roll, and left to sitfor a period of 72 hours. The results are shown below: 20% Antifog 40%Antifog Material Test Data Masterbatch Masterbatch As Made PE SurfaceContact Angle <10° <10° Antifog Performance Rating 8 9 After PE SurfaceContact Angle   32°   40° Contact Antifog Performance Rating 8 9

Example 4 (Comparative)

[0065] The sealant film (with an antifog wash coat) was similarlylaminated to a biaxially oriented nylon 6 film as described in Examples1-3, formed into rolls, and left to sit for a period of 72 hours. Theresults are shown below: After After After Contact Contact Contact Aswith Ex. 1 with Ex. 2 with Ex. 3 Material Test Data Made Film Film FilmExample 4 PE Surface <10° 65° <10° <10° Contact Angle Antifog 9 3 8 9Performance Rating

[0066] As is clearly demonstrated in the examples, the use of theprotective coatings of this invention can greatly diminish the transferof the active antifog component from the polyethylene surface, to thenylon surface of a polyethylene/nylon skinned structure.

[0067] While the present invention has been particularly shown anddescribed with reference to preferred embodiments, it will be readilyappreciated by those of ordinary skill in the art that various changesand modifications may be made without departing from the spirit andscope of the invention. It is intended that the claims be interpreted tocover the disclosed embodiment, those alternatives which have beendiscussed above and all equivalents thereto.

What is claimed is:
 1. A multilayered film comprising: a) a nylon filmhaving first and second surfaces; b) a sealant film, positioned on thefirst surface of the nylon film, either directly on the first surface ofthe nylon film or via an intermediate adhesive; c) an antifogcomposition contained within at least part of the sealant film or coatedon a surface of the sealant film opposite the nylon film; and d) aprotective film applied onto the second surface of the nylon film. 2.The film of claim 1 wherein the antifog composition is contained withinat least part of the sealant film.
 3. The film of claim 1 wherein theantifog composition is coated on a surface of the sealant film.
 4. Thefilm of claim 1 wherein the sealant film is directly attached to thefirst surface of the nylon film.
 5. The film of claim 1 wherein thesealant film is attached to the first surface of the nylon film via anintermediate adhesive.
 6. The film of claim 1 wherein the sealant filmcomprises polyethylene.
 7. The film of claim 6 wherein the polyethyleneis selected from the group consisting of ultra low density polyethylene,low density polyethylene, linear low density polyethylene, metallocenelinear low density polyethylene, medium density polyethylene and highdensity polyethylene.
 8. The film of claim 1 wherein the polyethylenelayer comprises a low density polyethylene.
 9. The film of claim 2wherein the sealant film comprises an antifog composition within apolyethylene layer, an ethylene vinyl alcohol layer and at least oneadditional layer.
 10. The film of claim 2 wherein the sealant filmcomprises a polyethylene layer, an ethylene vinyl alcohol layer and anantifog composition within another polyethylene layer.
 11. The film ofclaim 2 wherein the sealant film comprises a combination of a heatsealable polyolefin layer, a first polyethylene layer, an adhesive tielayer, an ethylene vinyl alcohol layer, another adhesive tie layer, asecond polyethylene layer, and an antifog composition within a thirdpolyethylene layer.
 12. The film of claim 11 wherein the polyolefinlayer comprises an alpha-olefin monomer having from about 2 to about 6carbon atoms.
 13. The film of claim 11 wherein the adhesive tie layer isselected from the group consisting of polyurethanes, epoxies,polyesters, acrylics, anhydride modified polyolefins and combinationsthereof.
 14. The film of claim 1 wherein the nylon film comprises nylon6, nylon 66, nylon 6/6,6 or combinations thereof.
 15. The film of claim1 wherein the nylon film comprises nylon
 6. 16. The film of claim 1wherein the antifog composition comprises one or more materials selectedfrom the group consisting of glycerol monoesters of a saturated orunsaturated fatty acid having from about 8 to about 20 carbon atoms,glycerol diesters of a saturated or unsaturated fatty acid having fromabout 8 to about 20 carbon atoms; ionic surfactants having phosphate,sulfate or quaternary amine functional end groups; and sorbitan esters.17. The film of claim 1 wherein the protective film is selected from thegroup consisting of polyvinylidene chloride, polyurethanes, aminemodified polyurethanes, epoxies, polyesters, acrylics, polyols andcombinations thereof.
 18. The film of claim 17 wherein the nylon filmcomprises nylon 6, nylon 66, nylon 6/6,6 or combinations thereof. 19.The film of claim 1 wherein the protective film comprises apolyurethane.
 20. The film of claim 1 wherein the nylon film isuniaxially oriented, biaxially oriented or a blown film.
 21. The film ofclaim 1 wherein the protective film is coated onto the nylon film. 22.The film of claim 5 wherein the intermediate is selected from the groupconsisting of polyurethanes, epoxies, polyesters, acrylics, anhydridemodified polyolefins and combinations thereof.
 23. The film of claim 1wherein said nylon film comprises a combination of a first nylon layer,an ethylene vinyl alcohol layer and a second nylon layer.
 24. The filmof claim 1 which is heat shrinkable.
 25. The film of claim 1 which has alength and a width and which is shrinkable by an amount of from about 2%to about 30% in its length or its width or each of its length and width.26. The film of claim 1 further comprising printed indicia on the nylonfilm.
 27. The film of claim 1 which has an oxygen transmission rate ofabout 0.05 cc/100 in²/day or less.
 28. The film of claim 1 furthercomprising a layer of polyvinylidene chloride on a surface of theprotective film.
 29. A roll of the multilayered film of claim
 1. 30. Amultilayered film comprising: a) a first nylon layer having first andsecond surfaces; b) an ethylene vinyl alcohol layer positioned on thefirst surface of the nylon layer; c) a second nylon layer positioned ona surface of the ethylene vinyl alcohol layer opposite the first nylonlayer; d) a polyethylene sealant film, positioned on a surface of thesecond nylon layer which is opposite to the ethylene vinyl alcohollayer; e) an antifog composition contained within the sealant film orcoated on a surface of the sealant film which is opposite the secondnylon layer; and f) a polyurethane protective film applied on the secondsurface of the first nylon film.
 31. The multilayered film of claim 30wherein at least one of said first and second nylon layers comprisesnylon
 6. 32. A process for forming a multilayered film comprising: a)positioning a sealant film onto a first surface of a nylon film, whereinthe sealant film has an antifog composition which is either incorporatedtherein or coated on a surface of the sealant film opposite the nylonfilm; and b) applying a protective film onto a second surface of thenylon film.
 33. The process of claim 32 wherein the nylon film andsealant film are coextruded.
 34. The process of claim 32 wherein thenylon film and sealant film are laminated together optionally via anintermediate adhesive.
 35. The process of claim 34 wherein the nylonfilm is biaxially oriented.
 36. The process of claim 32 wherein anantifog composition is incorporated in the sealant film.
 37. The processof claim 32 wherein an antifog composition is coated onto a surface ofthe sealant film opposite the nylon film.
 38. A food package whichcomprises a container having an open portion and a multilayered filmsealing the open portion, which multilayered film comprises: a) a nylonfilm having first and second surfaces; b) a sealant film, positioned onthe first surface of the nylon film, either directly on the firstsurface of the nylon film or via an intermediate adhesive; c) an antifogcomposition contained within at least part of the sealant film or coatedon a surface of the sealant film opposite the nylon film; and d) aprotective film applied onto the second surface of the nylon film; themultilayered film being positioned such that the protective film is awayfrom the open portion of the container.
 39. The food package of claim 38wherein the nylon film comprises nylon
 6. 40. A packaged food whichcomprises the food package of claim 38 and a food product in the foodpackage.
 41. The packaged food of claim 40 wherein the food productcomprises a meat.